IP television or IPTV is the name given to a range of services which allow television to be delivered over an IP network. IPTV is a service which will likely be facilitated by the so-called IP Multimedia Subsystem (IMS). IMS is the technology defined by the Third Generation Partnership Project (3GPP) to provide IP Multimedia services over mobile communication networks (3GPP TS 22.228, TS 23.218, TS 23.228, TS 24.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329 Releases 5 to 7), although the IMS architecture is such that its services can be accessed and controlled via other interfaces, for example the Internet. IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between user terminals, or user terminals and application servers. The Session Description Protocol (SDP), carried by SIP signalling, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to-user protocol, IMS allows operators and service providers to control user access to services and to charge users accordingly.
Due to the flexible nature of an IP network, IPTV will allow for a much more personalised service to users, e.g. video-on-demand, with information delivered to users over unicast IP streams. However, to order and control these user specific services, the user would normally be expected to use his or her remote control whilst sitting in front of a Set-Top-Box/TV. Such an approach would not allow users to take advantage of the mobility which should be facilitated by the IMS.
Solutions which allow a user to remotely access television services delivered to a specific location, via an IP connection to that location, are available. These typically require a home gateway which distributes television service from, for example, a cable modem, to user terminals over the Internet. Examples include LocationFree™ TV from Sony Corporation or the Slingbox™ from Sling Media.